The present invention relates to an electroplating machine having a plurality of cathode electrodes which are simultaneously brought into contact with a matter to be electroplated, at a corresponding number of contact points, and more specifically to a detector for detecting a contact resistance anomaly in the plurality of cathode electrodes of the electroplating machine.
In a Cu damascene interconnection forming process in a semiconductor device fabricating line, before a CMP (chemical mechanical polishing) step after an electroplating step, a film thickness of a Cu plated film is preferred to be as uniform as possible along a concentric circle. For the purpose of meeting with this demand, it is the present tendency to increase the number of contact points, namely, the number of cathode electrodes provided in a Cu electroplating machine.
However, since an in-plane distribution of the Cu plated film thickness greatly depends upon a contact resistance between each of the cathode electrodes and a wafer to be electroplated. Namely, if the contact resistance varies, the Cu plated film thickness correspondingly greatly varies. As a result, with an increase in the number of cathode electrodes, it has become difficult to make the Cu plated film thickness uniform along a concentric circle.
In order to overcome the above mentioned problem, it is necessary to measure the contact resistance between each of the cathode electrodes and the wafer to be electroplated, and to adjust the cathode electrode presenting a high contact resistance so that the contact resistance of all the cathode electrodes becomes uniform.
In a conventional measuring method, however, a testing wafer is used which has a metal film coated on the whole surface of the testing wafer. Therefore, only one contact resistance between the testing wafer and all the cathode electrodes can be measured, and therefore, it is impossible to identify the cathode electrode presenting an inadequate or defective contact with the wafer.
Therefore, in the Cu electroplating machine having a number of cathode electrodes, there are now demanded a method and a device capable of identifying the cathode electrode presenting an inadequate or defective contact.
Accordingly, in order to overcome the above mentioned problems of the prior art, it is an object of the present invention to provide a detector for detecting a cathode electrode presenting an inadequate or defective contact, in an electroplating machine having a plurality of cathode electrodes.
Another object of the present invention is to provide a means capable of individually measuring a contact resistance of each cathode electrode in an electroplating machine having a plurality of cathode electrodes, thereby to find out a cathode electrode presenting a contact resistance anomaly.
The above and other objects of the present invention are achieved in accordance with the present invention by a detector for detecting a contact resistance anomaly in a plurality of cathode electrodes provided in an electroplating machine which is so configured that the plurality of cathode electrodes are simultaneously brought into contact with a matter to be electroplated, the detector including a testing wafer having a plurality of metal films formed thereon separately from each other so that the plurality of cathode electrodes can be individually brought into contact with the plurality of metal films, respectively, and a measuring means for measuring a contact resistance between each of the plurality of cathode electrodes and a corresponding one of the plurality of metal films when the plurality of cathode electrodes are individually brought into contact with the plurality of metal films, respectively.
With the above mentioned arrangement, since the plurality of metal films are formed on the testing wafer, separately from each other, the plurality of cathode electrodes can be individually brought into contact with the plurality of metal films, respectively. Therefore, when the plurality of cathode electrodes are individually brought into contact with the plurality of metal films, respectively, the measuring means can measure a contact resistance between each of the plurality of cathode electrodes and a corresponding one of the plurality of metal films, without being influenced by a contact condition of the other cathode electrodes. Accordingly, it is possible to identify the cathode electrode showing an extremely high contact resistance, which can be deemed to be a cathode electrode presenting an inadequate or defective contact when the cathode electrode was actually brought into contact with a matter to be actually electroplated. Therefore, by adjusting the cathode electrode presenting an inadequate or defective contact, the contact resistance of all the cathode electrodes can be made uniform when the cathode electrodes are actually brought into contact with a matter to be electroplated in the electroplating machine, with the result that an in-plane distribution of the plated film thickness can be made uniform. Namely, it is possible to obtain the plated film having a film thickness uniform along a concentric circle.
In a preferred embodiment, each of the plurality of metal films includes a contact point to which a corresponding one of the plurality of cathode electrodes is brought into contact, and a measuring point to which one end of the measuring means is brought into contact, for measuring at the contact point the contact resistance of the corresponding one of the plurality of cathode electrodes.
In one embodiment, the testing wafer has at least one intervening film formed thereon, and the plurality of metal films are formed on the at least one intervening film. The at least one intervening film can be formed of a material selected from the group consisting of Ta, TaN, Ti and TiN.
Each of the metal films can be formed of a single metal layer, or a plurality of laminated metal layers. Each of the metal films can be formed of a material selected from the group consisting of Cu, Al, AlCu and W.
Furthermore, the testing wafer can be formed of a silicon wafer.